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LEDs go for a spin in POV displays

Jul 01, 2011

Most of us have probably seen simple persistence of vision (POV) displays that rotate a few LEDs on fan blades. Coin Mechanisms Inc. has taken the idea further with a POV display aimed at gaming and retail displays. Its spinning LED POV sign rotates 96 LEDs at between 1,000 and 1,250 RPM creating a palette for graphics and text equivalent to a fixed array of LEDs 96-pixels high and 256-pixels wide. The vertical height of the display image is 5.75-in and it can be viewed in a 360° circle from its 9.5-in-diameter/30-in-circumference viewing area.

To keep track of the position of the spinning LEDs, the device uses a slotted optic on the lower fixed platform interrupted by flags on the spinning platform. A Zilog Z8 Encore processor monitors the platform position and adjusts the motor speed to keep the display in sync. Developers say they used the Z8 Encore because its direct register-to-register architecture keeps housekeeping overhead to a minimum and reduces the program memory requirement. The processor also implements a real-time clock so date and time can be displayed, and the clock can be used as a timer to turn the display on and off at various times.

Coin Mechanism developers say the LEDs on the display are RGB-style devices, the smallest on the market. The small size of these devices made practical the 96×256 display resolution. The limiting factor for the number of images the display can handle is the flash memory. The whole display could be scaled up if need be through use of larger flash memory. The basic display consumes about 44 W, though add-ons and options can make that figure rise to 74 W.